Combiner.java revision 60fbf9e9627063ad697809d62853f6b3ee5f6ad3 
1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.inputmethod.event;
18
19import java.util.ArrayList;
20
21/**
22 * A generic interface for combiners. Combiners are objects that transform chains of input events
23 * into committable strings and manage feedback to show to the user on the combining state.
24 */
25public interface Combiner {
26    /**
27     * Process an event, possibly combining it with the existing state and return the new event.
28     *
29     * If this event does not result in any new event getting passed down the chain, this method
30     * returns null. It may also modify the previous event list if appropriate.
31     *
32     * @param previousEvents the previous events in this composition.
33     * @param event the event to combine with the existing state.
34     * @return the resulting event.
35     */
36    Event processEvent(ArrayList<Event> previousEvents, Event event);
37
38    /**
39     * Get the feedback that should be shown to the user for the current state of this combiner.
40     * @return A CharSequence representing the feedback to show users. It may include styles.
41     */
42    CharSequence getCombiningStateFeedback();
43
44    /**
45     * Reset the state of this combiner, for example when the cursor was moved.
46     */
47    void reset();
48}
49